This invention relates to a pressure tester for automotive engine cooling systems and a method for pressure testing such systems.
The cooling system of conventional automobiles comprises a radiator, an engine block having flow paths therein and a water pump which are all connected by conduits for circulating coolant. The water pump is usually attached to the lower front of the engine and communicates with the flow paths therein. In general, a lower radiator conduit connects the water pump and the bottom of the radiator, and an upper radiator conduit connects the upper end of the engine flow paths and the top of the radiator, thereby effecting a complete flow circuit through the engine and the radiator. A thermostat is usually placed in the cooling system at the top of the engine near the upper radiator conduit to block water circulation when the engine is operating below desired temperatures.
A heater is also included in the cooling system of most automobiles, and is generally located near or in the interior of the automobile. The heater is usually connected to the other parts of the cooling system by a heater-supply conduit slipped tightly over a nipple fitted in a heater supply aperture on the top of the engine and over a nipple on the heater, and by a heater-return conduit connected to the heater and emptying into the water pump.
It is well known that automotive cooling systems should be pressure tested periodically in order to detect leaks in the system. As the engine temperature rises during operating the temperature of the coolant in the system will also rise. Since the cooling system is completely enclosed, the pressure within the system will rise in relation to the temperature rise of the coolant. Minor leaks present in the system may result in excessive loss of coolant as the pressure rises in the system. The more coolant that is lost, the less capability the cooling system has for keeping the engine temperature from rising above a normal operating level. This could result in engine overheating and damage to the engine parts.
The common method of pressure testing an automotive cooling system utilizes a hand operated air pump which is attached to the radiator filler neck after the radiator cap has been removed. Air is pumped into the cooling system until the desired pressure level is attained. The pressure level is usually indicated by a gauge attached to the air pump. The cooling system is checked for leakage by observing the gauge indicator. If the indicator holds steady at the test pressure level, normally the usual operating pressure of the system, this would indicate that the system will hold pressure and therefore there are no leaks. If the gauge indicator drops from the test pressure level, this would indicate a loss in pressure and therefore a leak. If a leak is indicated an inspection of the cooling system is made for escaping liquid.
The radiotor cap "opening pressure" is tested separately by attaching the cap onto a special adapter for pressurizing with the same hand pump. The pressure is increased until the pump pressure gauge indicates the cap opening pressure by a sudden drop in the pressure. The actual pressure at which the cap will release is then compared to the cap set pressure, i.e., the pressure at which the cap is supposed to open, to determine if the pressure cap is functioning properly.
It will be seen that in utilizing the above method for pressure testing an automotive engine cooling system the radiator cap must be pressure tested independently of the rest of the engine cooling system. As a consequence, this method has proved to be very time consuming. It is also not totally accurate in giving a true picture of the pressure reliability of an engine cooling system under normal operating conditions, since the test procedure does not indicate whether the radiator cap is seated properly on the radiator filler neck. Unless the radiator cap is seated properly on the radiator filler neck, leakage will occur under cooling system operating conditions. Therefore, it is essential that the radiator cap be pressure tested while in place on the filler neck seat in order to insure the pressure integrity of the whole engine cooling system.
A radiator overflow tube is normally provided in an automotive engine cooling system. One end of the tube is affixed to the radiator filler neck in such a manner that when the pressure in the system builds up above the cap opening pressure, the main valve in the cap will lift off its seat and allow the pressure to release through an outlet in the filler neck to which is attached the overflow tube. The other end of the tube vents to the atmosphere. It is essential to check the radiator overflow tube for blockage to insure safe operation of the cooling system. In the event that pressure must be released the tube must be clear to prevent serious damage to the cooling system. When using the method described herein above, the pressure release capability of the radiator overflow tube is not tested. The hand operated air pump is attached in such a manner to the radiator filler neck that the outlet to the radiator overflow tube is covered by the pump mechanism during the test.
If a leak is indicated using the hand operated air pump and gauge, it is not always readily ascertainable where the leak is located. The normal engine cooling system is liquid filled except for a small volume of air located at the top of the radiator, the highest point in the system. The air pressure in this portion of the radiator is increased by the hand pump which is connected to the radiator filler neck at the top of the radiator. Therefore, any leak which may occur in the air-filled section of the radiator can only be detected by the presence of escaping air which cannot be observed by a visual inspection.
U.S. Pat. No. 3,650,147 which issued on Mar. 21, 1972 to Robert G. Moyer, entitled "Cooling System Pressure Tester" discloses a cooling system pressure tester wherein the pressure is allowed to rise slowly as it is observed on a pressure gauge and when the pressure reaches the desired level, the high pressure water supply is manually shut off by a valve. In the present invention, on the other hand, the pressure rise is generally not observed because a gauge is not required.